Known machines of the above type, one of which is described for example in U.S. Pat No. 4,848,371, were substantially designed for the sole purpose of making rolling speed—i.e. the speed at which said groups are rotated about their axes during the rolling operation—at least partly independent of the rotation speed of the rolling unit about said first axis, and so enabling filter-tipped cigarettes to be produced at output rates which would be impossible if the two speeds were directly interdependent.
Though capable, for a given output rate, of performing the rolling operation at fairly slow speed, known machines of the above type have several drawbacks, mainly due to the suction rollers being activated by a single epicyclic gear train, in which a drive member (sun gear, carrier or ring gear) is powered directly by a drive shaft of the rolling unit, and the planet gears are connected angularly to the suction rollers. In other words, as opposed to being independent, the rolling speed and the rotation speed of the rolling unit of known machines of the above type are actually related by a given reduction ratio, and, above all, if the rotation speed of the rolling unit is constant, the same also applies to the suction rollers.
As a result, known machines of the above type are fairly “rigid” as regards sizing of the rolling unit, location of the rolling unit with respect to the feed and output drums, and selection of the rotation speeds of the rolling unit and suction rollers. Moreover, in known machines of the above type, the spacing of the groups supplied to the rolling unit, which is normally equal to the width of the connecting bands used to form the double cigarettes, is always equal to the spacing of the double cigarettes supplied to the output drum, and rolling initiation speed—i.e. the speed at which each group is fed into the relative rolling channel—cannot be adjusted.